The major objective is to isolate and characterize in vitro human helper T cell clones (TH) which recognize autologous Epstein-Barr virus-transformed B lymphoblastoid cell lines (aEBV-BCL). These TH will recognize EBV-induced cell surface antigens in conjunction with human Ia molecules on the BCL. Thus, an in vitro system will be developed which will allow the study of the initiation of specific immune responses to EBV at the cellular and immunogenetic level. Further, the two cell lines involved (TH and EBV-BCL) will be homogeneous and provide a readily available source of material for the biochemical and molecular genetic study of the molecules involved in this specific cellular interaction. The specific aims of the project are (1) to define LYDMA, that is EBV-induced antigen(s) involved in TH responses (2) to investigate the mechanisms of antigen presentation and Ia restriction involving EBV-induced antigens (3) to determine how T cells and/or T cell factors regulate EBV infection and transformation of B cells in vitro (4) to probe the cell surface molecules involved in aims 1-3 via monoclonal antibodies. Immune response involving EBV are highly relevant to a number of clinical syndromes. These include 1) Infectious mononucleosis (IM), 2) Burkitt's lymphoma (BL), 3) X-linked lymphoproliferative disease (XLP), 4) Rheumatoid arthritis (RA) and, possibly, 5) Acquired immune deficiency syndrome (AIDS). Each of these syndromes involves significant clinical and/or laboratory anomalies of the immune system in which TH specific for EBV almost certainly participate. After information is obtained on EBV-specific TH from normal subjects, attention will be turned to investigating TH responses in these specific disease states. The methods involved in this project are primarily applications of recently developed techniques. T cell cloning and monoclonal antibody production will produce the necessary cellular and biological reagents. The system will then be analyzed by cell proliferation assays, RIA and ELISA, immunoprecipitation and "Western" blotting, and fluorescence flow cytometry (FACS). EBV-BCL and EBV-specific TH cell clones will be co-cultured to measure T cell proliferation and B cell antibody secretion. The effects of mcAbs made against the two cell lines will be tested by adding to co-cultures. Antibodies that alter T or B cell function will be used to study biochemically the cell surface molecule(s) involved.